There is huge stigma around those of us who experience abuse or violence from our children, so most people don't share widely the fact of its existence.
I have an ND teen who verbally abuses me, physically assaults me and damages our house during meltdowns. He's never engaged in any physical sexual abuse, but I am subjected to pretty horrible verbal sexual comments during meltdowns.
In our case, exposure to porn has been the biggest factor. We thought we were doing okay as he only used the internet in family rooms where I was present, but he was watching things with the sound off and his screen facing away from me.
Our first indicator that he has been accessing porn is that he starts engaging in misogynistic and verbal sexual abuse, which is usually accompanied by physical attacks. This has been so much better since really tightening up our parental controls on devices.
I can only imagine how horrific it must be to be on the receiving end of physical sexual abuse from your child.